1. Field of the Invention
The present invention relates to a ratcheting device and more particularly to a diopter adjustment device.
2. Related Art Statement
A diopter adjusting mechanism incorporating a ratchet device for locating the position of a diopter adjusting dial has been disclosed in Japanese unexamined patent publication No. H1-291227. This diopter adjusting mechanism has a rotatable cylindrical cam ring integral with an adjusting dial for diopter adjustment. A series of grooves are provided on the outer circumference of the cam ring, and a ratchet ball is disposed in such a manner that it always contacts and slides on the groove like a pawl. When the adjusting dial is rotated, the position of the dial can be located with the ratchet device.
However, the ratchet device incorporated in the above-described diopter adjusting mechanism makes it difficult to configure an apparatus like a camera with a small size because the ratchet grooves provided on the cylindrical cam ring increase the space occupied by the device.
Other conventional ratchet devices constituted by a rotary member occupying a ball space and having simple structures include ratchet devices having a ratchet ball provided on a rotary member such that it moves to draw an arcuate locus on a plane and having ratchet grooves provided on a fixed member on which the ball slides. The grooves of such a ratchet device are disposed in a radial configuration on a plane of the fixed member.
In the case of the above-described ratchet device, however, the area of the fixed member where the grooves are formed must be released from the molding die in which it is formed in a direction orthogonal to the plane of the grooves because the grooves are disposed in a radial configuration. This makes it necessary to use a slide die and can reduce productivity.
The present invention has been conceived to solve the above-described problem, and it is an object of the invention to provide a ratchet device which has a simple structure, whose components can be easily manufactured and which can be made compact.
According to an aspect of the invention, there is provided a ratchet device having a rotary member rotated about a rotary shaft, a base member for rotatably supporting the rotary member, a contact member provided between the rotary member and base member and an urging member. The base member has a plurality of linear ratcheting grooves which are provided on a surface orthogonal to the rotary shaft and which extend in parallel with each other.
In the ratchet device, the rotary member is in contact with the contact member which is in contact with the grooves for ratcheting movement. When the rotary member is rotated, the contact member moves over the grooves resulting in a ratcheting operation.
According to another aspect of the invention, there is provided a ratchet device having a rotary member rotated about a rotary shaft, a base member for rotatably supporting the rotary member, a contact member provided between the rotary member and base member and an urging member. The base member is formed using injection molding, such that the parting line forced during the injection molding process passes through the center of the rotary shaft. The base member has ratcheting grooves forming part of the ratchet mechanism. The grooves are parallel linear grooves which are provided on a surface orthogonal to the rotary shaft so as to be orthogonal to the parting line. The urging member urges the rotary member into contact with the contact member which is in turn urged into contact with the ratchet grooves.
In the ratchet device, when the rotary member is rotated, the contact member moves over the ratchet grooves, resulting in a ratcheting operation.
According to still another aspect of the invention, there is provided a ratcheting device for a camera having a manually operated operating member, a molded ratcheting member having ratcheting grooves and a contact member sliding in contact with the ratcheting grooves as the operating member is rotated. The ratcheting grooves on the ratcheting member are provided on a surface extending perpendicular to a parting line on the ratcheting member which is created during the molding operation.
In the ratchet device for a camera, when the operating member is rotated, the contact member moves across the grooves, resulting in a ratcheting operation.